This invention relates to equipment for detecting and measuring microorganisms in liquids. The equipment is particularly useful for detecting microorganisms such as white and red blood cells in urine.
A known method for detection of microorganisms in urine is to incubate a sample and then detect microorganisms using conventional techniques. The process is time consuming as it needs to be done on an individual basis and requires the use of skilled staff both to carry out the test and to interpret the results.
Particle counters of the Coulter Counter type may be used to detect particles in liquids as described in the Journal of Chemical Pathology, Vol. 32, pps 386-390 (1979 Published by the BMA, London, England). is drawn through an orifice into the counter and the particles counted across the orifice. We have found that in some biomedical applications small orifices which give good sensitivity are prone to become blocked by debris and that larger orifices lack sensitivity.
For example it has been found that when orifices are of a size, e.g. 30-50 micrometers, they can be blocked. The orifice can be made larger e.g. at least 50 micrometers or preferably at least 100 micrometers. A larger orifice, however, can reduce sensitivity.